The objective of this proposal is to obtain cellular populations enriched in rat gastric mucosal cells associated with histamine metabolism for physiological and biochemical studies. Isolated-cell suspensions from rat gastric mucosa will be prepared followed by a variety of cell fractionation methods. The following parameters will be assessed in mixed, isolated-cell preparations from the gastric mucosa: histamine decarboxylase (HDC), histamine content (Hm), histamine binding capacity (HR), histamine methylating enzyme (HME) and histaminase (Hase). Radioactive histamine and histidine will be administered to an additional group of rats, prior to gastric cellular fractionation, and the presence of radioactivity traced as an additional marker for cells involved in histamine and/or histidine uptake, storage and metabolism. Having determined the baseline levels of these markers in mixed-cell preparations, the marker levels will be determined in cells subjected to fractionation procedures to ascertain the degree of enrichment. The optimal conditions for separation of specific cell types will be determined utilizing computer programs. Once viable enriched fractions of gastric cells have been isolated a morphological and viability study will be performed. The fractions containing radioactivity will be compared with the non-radioactive fractions containing known biochemical activities to determine their correlation. Preliminary analysis by thin-layer chromatography will be performed searching for degradation products of histamine in pertinent radioactive fractions. It is expected that this investigation will provide needed information about the cellular types involved in histamine metabolism in gastric mucosa as well as provide working populations of viable cells enriched in specific types adequate for functional studies.